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Digital Item Adaptation

MPEG-21 Digital Item Adaptation

MPEG doc#: N8083Date: April 2006Author:

1 Introduction

The last decade has brought an enormous growth of digital multimedia content. This has also led to a vast diversity of media formats but also came with an increased richness of audiovisual content and services that now include carefully composed sets of scene representation, audio and speech, video and graphics data.

At the same time, the multitude of devices for accessing and interacting with multimedia content has grown significantly. The spectrum ranges from Personal Computers (PCs) and Set-Top Boxes (STBs) to portable devices like Personal Digital Assistants (PDAs) and mobile phones. Each device may be constrained in a different way, such as in terms of display size, color capabilities, input options, processing power, memory resources and power supply.

Finally, a wide spectrum of networks for the transmission of multimedia content has emerged. In particular, wireless networks and broadband access technologies have proliferated in recent years, enabling users to access the Web and multimedia content from different locations, in different contexts, and with varying connectivity characteristics.

These continuing trends as well as additional factors, like specific preferences or impairments of the users, represent major barriers towards the successful deployment of compelling multimedia services, such as:

the content and service providers are burdened with high costs for creating, managing and offering a multitude of versions of the same content in order to match the most relevant usage conditions

the network providers are burdened with high costs for transcoders and transraters in their gateways

the users will not experience the best possible service since an optimum match to the usage condition will not be achieved

2 DIA overview

In emerging multimedia services, content is more and more exchanged bundled with associated metadata, such as Digital Rights Management related information. To cope with this new type of content, the MPEG-21 framework introduces the concept of Digital Item, which encompasses the multimedia resource and associated metadata. MPEG-21 DIA was designed as part of the overall MPEG-21 framework, by providing tools that interface consistently with this MPEG-21’s Digital Item concept. Furthermore, MPEG-21 DIA was built in a modular way such that its various tools may be used independently from each other and for usage scenarios beyond MPEG-21.

MPEG-21 DIA specifies a comprehensive set of description tools that can be exchanged and used for enabling the optimized adaptation of multimedia content. DIA descriptions are specified in the widely used XML language facilitating the development of applications creating, aggregating, exchanging and consuming the descriptions. Whenever bandwidth is constrained, an efficient XML encoding technique is provided by the MPEG-B standard [5].

Describing the usage context is required for determining what version of the content optimally fits this context. For this purpose, DIA provides a set of metadata describing the context in terms of networks and devices characteristics, user preferences as well as natural environment characteristics. These metadata are gathered under the term Usage Environment Descriptions.

Additionally, DIA specifies content centric metadata facilitating the content adaptation process itself. Firstly, DIA provides a way to express the correspondence between usage context and content characteristics, resulting in possible adaptation operations required for obtaining the optimized version. Secondly, it provides the means to perform content adaptation in an efficient and coding format independent way. In particular, MPEG-21 DIA leverages the use of scalable content such as MPEG-4 Scalable Video Coding (SVC) REF _Ref128471928 \r \h [6] by specifying a generic tool for describing the high level bitstream syntax and using this description in order to obtain a new adapted version.

3 Benefits of Digital Item Adaptation

Service and Content Providers, Network Operators, Device Manufacturers and End Users benefit from MPEG-21 DIA. This standard has been designed in a protocol and application independent way, and therefore can be used in any application domain.

In particular, Service and Content Providers are facing the question: how can the same content be brought to the largest possible audience? By allowing the content to be adapted to the diverse usage environments, MPEG-21 DIA tools allow Content Providers to avoid creating, re-encoding and managing multiple versions of the same content, and hence to reduce their content management cost. For Service Providers, MPEG-21 DIA lowers the entrance barriers for new delivery channels, enabling more ways to reach consumers.

In particular, MPEG-21 DIA leverages the use of emerging scalable multimedia formats, such as MPEG-4 SVC and save the cost of transcoding the content. Additionally, being media format independent, it is a future-proof solution.

Network Operators can for themselves significantly reduce their equipment and operation costs of content adaptation by using the generic approach of MPEG-21. For example, a single MPEG-21 codec-agnostic adaptation engine needs to be deployed once and can be used for multiple existing and future coding formats.

For Device Manufacturers, MPEG-21 DIA provides a rich and extensible vocabulary for describing the capabilities of their devices enabling interoperability with Network Operators, Service and Content Providers.

Lastly, Consumers using MPEG-21 DIA-enabled devices and services will enjoy an improved experience anywhere, anytime, and with any device.

4 Further reading

The MPEG-21 Digital Item Adaptation standard (ISO/IEC 21000-7 [1]) has been finalized in 2003 and can be obtained from the International Standardization Organization (ISO). A first amendment called Conversions and Permissions [2] has been finalized in 2005. It provides new tools declaring adaptation operations such as summarizing a video into a sequence of images. A second amendment [3] is in progress to extend the DIA tools for Dynamic and Distributed Adaptation.

A Java reference software described in ISO/IEC 21000-8 [4] and demonstrating the creation and use of DIA descriptions is also available from ISO.

Lastly, a number of scientific publications provide more detailed insight on MPEG-21 DIA. In particular, the MPEG-21 Book [7] covers the different parts of the MPEG-21 framework, including DIA. IEEE Transactions on Multimedia has published a special issue on MPEG-21 (see [8] for an overview of DIA). Additional resources may be found on the following web sites [9] and [10].